A wet construction method is known as a construction method for forming a coating film on surfaces of walls, floors, ceilings, and the like of a building with a coating material such as a plastering material. In the wet construction method, a wet coating material in the form of slurry is obtained by kneading a composition containing an inorganic powder such as mortar, lime plaster, gypsum, or diatomaceous earth as a principal with water, and a coating film is formed by a method such as coating the surface of an interior decoration wall, an exterior decoration wall, and the like of a building with the wet coating material using a trowel (trowel coating). Particularly as a coating material for finishing an interior decoration wall or an exterior decoration wall of a building, lime plaster-based coating materials and gypsum-based coating materials are widely used in order to secure design characteristics of wall surfaces. Generally, these wet coating materials are each made into a product as a composition in the form of a powder, and the product is used by being kneaded with water at a construction site.
For example, Patent Literature 1 discloses a method for suppressing color skipping in a colored lime plaster coating film by using a colored lime plaster composition containing lime, a white pigment, a colored pigment, a binder, and water for forming a coating film. Patent Literature 2 discloses a coating material for a wall surface, the coating material obtained by blending an inorganic powder having a particle diameter of 0.1 mm or less, gypsum having a particle diameter of 0.1 mm or less, a fiber having a wire diameter of 5 to 15 μm and a length of 3 to 10 mm, a water-soluble paste material, and a synthetic resin each in a predetermined ratio. Patent Literature 3 discloses invention relating to a dry gypsum composition and a gypsum-based coating material each containing hemihydrate gypsum, a pigment, and a predetermined content ratio of a particular habit modifier, wherein the dry gypsum composition and the gypsum-based coating material are controlled so that dihydrate gypsum to be obtained through hydration of the hemihydrate gypsum becomes a plate-like crystal having an aspect ratio of 1 to 9.